Ryanair boss Michael O'Leary issued a warning to future holidaymakers as the foreign travel ban was lifted.
The budget airline reported a full-year loss of 815 million euros (£702 million) as traffic fell 81% from 149 million passengers to 27.5 million due to the pandemic.
But the Ireland-based low-cost airline said in a statement it expects to benefit from a "strong rebound of pent up travel demand" through the second half of 2021.
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Mr O'Leary said the airline was "very optimistic for the next couple of months" after bookings trebled during the past six weeks.
He told BBC Breakfast: "The UK vaccine programme has been extraordinarily successful. We're up to 60% of the adult population having received their first dose.
"European countries recognise that. They're beginning to lift restrictions on inbound UK visitors.
"Portugal this morning. We're very hopeful that Italy and Greece will be added to that green list before the end of May, and Spain will come shortly thereafter."
But Mr O'Leary warned that while fares will remain low this summer, they could soar in 2022 as the number of seats will be 25% lower than before the pandemic due to airlines collapsing or reducing their operations.
He said: "There's no doubt in my mind that prices will rise, particularly during the peaks of the bank holiday weekends, the school holiday travel period, but that won't affect bookings for summer 2021.
"In 2021 prices will never be cheaper because all the airlines are running with much lower advanced bookings than we have ever had before because of the travel restrictions.
"So I think this summer there are going to be great travel bargains. Get on the Ryanair website and book them now.
"But summer 2022, we will be urging people to book very early because I think there's less seats and pricing will be higher."
